Theoretical study on hydro-mechanical deep drawing process of bimetallic sheets and experimental observations

The application of hydroforming process on aluminum-steel laminated sheets includes advantages of both process and material to improve formability of lightweight low formable aluminum sheets. In this research, analytical models were developed to investigate stress analysis and instability condition in hydro-mechanical deep drawing (HMDD) of cylindrical AL/St cups. Based on these models, several parametric study were performed regarding to the effect of thickness of layers, setting condition of layers, drawing ratio and frictional condition on key parameter of critical fluid pressure of process. The experimental works were performed on Aluminum (1050-H0)/Carbon steel (St13) two-layer sheets for verification of analytical results and the prediction of actual working pressure window. It was demonstrated that the fluid pressure window for a successful part forming could be rapidly predicted with a reasonable accuracy by the analytic model compared to lengthy and costly FEA or experimental trial and error.

► We model the HMDD process of bimetallic sheets with two analytical approaches.
► The model predicts plastic instability of process and upper critical fluid pressure.
► The lay-up and thickness of sheets changed working fluid pressure zone.
► Increasing drawing ratio and friction coefficient will decrease critical pressure.
► The model estimates failure pressure, maximum punch force and formability of sheets.